AlterQuery  test2 (children 2)
 ExpressionList (children 1)
  AlterCommand ADD_COLUMN (children 1)
   ColumnDeclaration invalid_column (children 2)
    DataType String
    Function concat (children 1)
     ExpressionList (children 2)
      Identifier str
      Literal \'b\' (alias a)
 Identifier test2
